[Imp]

The details of using the op filter are in the online manual but yes generaly if I set it for armour & no RCL ATGM jeeps around I either limit range to close or set to ignore.
A platoon of 3 or 4 tanks if you really wanted to
Set 1 to engage Heavy armour only
1 or 2 to engage heavy armour & APCs
1 to engage everything
The choice is yours.

As I said apart from flame weapons rarely switch weapons off filter applies equally to troops.
But if you want to fire at soft targets with squads without using the RPG then switch it off.
Vs any armoured target just set the range if you want.
To be honest though most of the time I find routines work well enough but do set for certain situations.